A typical example of a conventional automatic tool change machine tool having a vertical column and a toolholder magazine is disclosed in the copending Japanese Utility Model Application No. 55-189828, filed on Dec. 27, 1980. In the conventional machine tool, a magazine in the shape of an annular plate storing a plurality of toolholders in receptacles is arranged on the side of the vertical column. A vertically movable tool bar is received in a saddle. The saddle is mounted so as to be laterally movable on a crossrail vertically movable along vertical guides formed in the front face of the vertical column. When a toolholder holding a cutting tool and attached to the tool bar is exchanged for a different toolholder stored in the magazine, the saddle together with the tool bar have to be first moved in the lateral direction along the crossrail until they come adjacent to the magazine. The exchange operation is then effected by vertical movements of the tool bar in the saddle. After completion of the exchange operation, the saddle along with the tool bar to which the new toolholder is attached have to be returned to the working position. Accordingly, a long time is taken for each exchange operation and the exchange mechanism is rather complex.